The effects of a series of ionic liquids, with systematic variations in the cation, on the condensation of an alkyl amine with an aromatic aldehyde were investigated, and the outcomes compared with those predicted based on related reactions. The addition of ionic liquids increased the observed rate constant; the mole fraction dependence of this increase was qualitatively consistent with predictions. Temperature-dependent kinetic analyses were used to demonstrate that the microscopic origins of the effects were as forecast, though the relative weighting of enthalpic and entropic contributions was dependent on the salt used.

The effect of a series of ionic liquids containing different anions (bis(trifluoromethanesulfonyl)imide, dicyanimide, hexafluorophosphate, tetrafluoroborate, and bromide) on the rate constant of a bimolecular substitution process was investigated. A general ionic liquid effect was noted, with increases in the rate constant observed in all ionic liquids used when compared with that in acetonitrile. Temperature-dependent kinetic data allowed calculation of activation parameters in each of the reaction mixtures considered; these parameters showed that the microscopic origins of the rate enhancements observed were not the same for all of the ionic liquids used, demonstrating the importance of the nature of the anion.

The polarisability of an ionic liquid is key in determining the rate constant of a unimolecular substitution process.

A series of ionic liquids containing anions of differing coordination strength were investigated as solvents for the condensation reaction of an alkyl amine and an aromatic aldehyde. As predicted, the rate constant of the process was found to increase with the proportion of the ionic liquid in the reaction mixture. Temperature-dependent kinetic analyses demonstrated that by varying the ability of the anion to interact with the cation the magnitude of both the enthalpy and entropy of activation could be controlled in a predictable manner, with the activation parameters being linearly dependent on the ionic liquid basicity. Interestingly, the unexpected trend in the rate constants observed when altering the anion of the ionic liquid highlighted the presence of more subtle secondary microscopic interactions involving the anion, further emphasizing the fragility of the enthalpy - entropy balance.

The nucleofugality of chloride has been measured in solvent mixtures containing ionic liquids for the first time, allowing reactivity in these solvents to be put in context with molecular solvents. Using well-described electrofuges, solvolysis rate constants were determined in mixtures containing different proportions of ethanol and the ionic liquid 1-butyl-3-methylimidazolium bis-(trifluoromethanesulfonyl)imide; the different solvent effects observed as the mixture changed could be explained using interactions of the ionic liquid with species along the reaction coordinate, determined using temperature dependent kinetic studies. The solvolysis data allowed determination of the nucleofugality of chloride in these mixtures, which varied with the proportion of salt in the reaction mixture, demonstrating quantitatively the importance of the amount of ionic liquid in the reaction mixture in determining reaction outcome. Nucleofugality data for chloride were determined in seven further ionic liquids, with the reactivity shown to vary over more than an order of magnitude. This outcome illustrates that the components of the ionic liquid are critical in determining reaction outcome. Overall, this work quantitatively extends the understanding of solvent effects in ionic liquids and demonstrates the potential for such information to be used to rationally select an ionic liquid to control reaction outcome.